I am now pretty interested in the CGS VCO, but am finding not a lot of info as to how others have built it. Surprising, as it seems to offer a hell of a lot of options to float most all folks boats.

Anyhow, I would love to hear some feedback about this oscillator. What parts did you implement, would you do it the same again?

I want to know more about the staricase section.

I've only built 1 of them and I attemplted to implement every single option. The only thing that wasn't / isn't working is the Staircase function. Though, I haven't debugged it either.
Outside of that, the VCO sounds wonderful, especially with it's waveshape control.
However, having 2 more of that VCO board, I'm building them for +/-5V Sawtooth only. (Same thing with my currently built Bi-N-Tic as well as my 2nd unbuilt Bi-N-Tic).
I'm going to be building my own waveform converters again in the near future. This way, keeping the VCOs simple, I'll be able to put 4 of them into a 3U 19" rack panel.

Quote:

Also has anyone used an Analog Devices 2210 in place of the 394? I have some 2210's that I got as samples before the clampdown, and would prefer to drop them in instead of hunting the 394s down.

I will definitely be using the waveshaper section, as I LOVE the skew on the Thomas Henry XR osc.

Lets hear about your VCOs...

I used the SSM2210 in my Bi-N-Tic as well as VCO from Ken. They worked wonderfully in both. As well as metalized polyester film caps for their 1nF positions. Solid tuning over quite a few octaves for both of them.

If you haven't bought 1 of those VCO PCBs from Ken yet - go for it! Wonderful piece of work from Ken! Well worth it.

I have been building two, but completing them has waited as i was missing a few resistor values. Having washed the boards, I'll let them dry today, and by weekend should be able to have the trimmers and styrene cap soldered in. And then, the big bench test! There are so many connections on these PCBs that I'll need notes handy to even remember what they are. So, I'll probably hear them this weekend!

Rykhaard wrote:

As well as metalized polyester film caps for their 1nF positions.

Hmmm.... I might just be too tired now, but I can't find 1nF caps on here! I used tantalum for the polarized caps, except an electrolytic for the 47uF. A polyester 4n7. Monolithic 100nF and ceramic discs for the pF values. I was guessing that the main timing cap was the crucial one to make stable. The decoupling caps I'd suppose needn't be great. I wonder about the pF caps if these might worsen the sound quality, since they have that reputation. Where are the 1nF? Tomorrow I'll recheck the schematic.

I hope to buy another few of these VCOs later, so maybe I'll compare the caps then. I can hardly wait!

The CGS VCO is incredible! I didn't leave off any options(besides the DC outputs) and I don't regret a thing.

With nothing connected to the staircase out acts as independent ramp lfo, the speed of which is controlled by the sub octave division knob(up the the low audio range) It is lots of fun to modulate the waveshape and frequency(with reversing attenuator) with this. Feed one of the outputs into it and you can modulate the VCO with divisions of it's own frequency.

Those are just a few fun things you do with the VCO all by itself._________________" I went through quite a few trannies til I found one I liked" - Wild Zebra

ive got one in cardboard, it has everything except the sub-osc. i had it with the sub-osc on a 3U panel but decided it could be condensed.

sorry for the bad picture

it is the one in the middle with the two big silver knobs

rolls like this,
big silver knobs - fine and coarse tune
small knobs at top - fm ac & dc with cv atten
small knob to the right of tune is pwm
small knob to the left of the tune is waveshape
small knob under tune is linear cv atten

Whoa! CLIFF is doing it! If I were still early in building my machine, I'd convert back! I'm prolly over 300 jacks now though in my machine, with the current panels being built so it'd be a little too costly now. Oh well.
Whether purchased or painted, they sure look great!

THAT reminds me - I want to email Johnson and see about the possibilities of getting a custom run of CLEAR banana jacks. Wondering what they'd want for a minimum order. (Then LEDs could be strung behind them / etc. )

im having a couple of stumbling blocks while trying to tune my cgs vco, i was wondering if there are some kids out there who have done this that can help me out.

ok so i disconnected my course and fine tune pots.
used the zero centre trim to pull voltage down to 0

then i grabbed 9v batter and scaled the current down to 1v with a pot.
i used a pot to do this and then ran the wiper and ground through a patch cable. first stumbling block. the voltage was measured at 1v without connection to the vco. (i had a dmm connected to the pot as well). Once i connected the patch the voltage dropped to 0.45V. It wasnt the pot turning by itself, as when i disconnected it, the voltage came back up to 1V. So im curious about this, do i need up up the voltage so it is 1V when it is connected? If someone could explain this for me it would be great.

so i assumed that i didnt need to re-scale the voltage and i tuned it roughly to a octave separation with the span trim. i used ableton's analog synth as a reference and did it by ear. i think i got it in there with only a few cents difference. i listened for a phasing effect and then tuned it a little more till it stopped and i got a unisen kinda sound.

anyway, so i didnt bother trying it for 3 octaves yet, i wanted to check what it was like, so i reconnected my tune pots and found that the range of the course pot was completely fuxed. The whole audio range was located in a degree or 2 of the pot. So this is obviously wrong.

ido i need up up the voltage so it is 1V when it is connected? If someone could explain this for me it would be great.

Yes, up it, you'll want 1 V at the control input of the osc for an octave. When the pot is a high value one the 100 k load or so (typically) of the input will make the voltage drop. A drop of over 50% is a lot though, did you use a 1 Meg pot or something? If so the large drop would make sense, maybe better use something like a 1 k pot - it should still drop a bit then but far less - I'd still up it then ... if possible and measurable on the DVM._________________Jan

Very nice, great idea painting the washers/nuts. What sort of paint? rustoleum?

Have you had them in use long enough to know if the paint scratches up much?

I just bought whatever brands had the colors I wanted, which just so happens was mostly rustoleum. I havent been using them very long, but I put them up to repeated scratch tests on a mock-up panel. I have to stab them pretty hard with a patch cord to get them to scratch. Scraping them with a force I am likely to use during patching produces no scratches even after many repetitions. Only time will tell If theyll hold up over the years, though._________________" I went through quite a few trannies til I found one I liked" - Wild Zebra

Hi, I´d lke to know what´s unique with the CGS VCO. It has many options but except that? does it sound very different?

One unique thing is the amount of features which you can interact with. It's based on the ASM-1 VCO, which is well-known as a stable, good-sounding sawtooth VCO which can be made easily without a lot of expensive parts. It has a handy CV processor on the input which is a hugely useful thing which most overlook. And it offers a monster waveshaper on the output for getting "nonstandard" waveforms.

It is not different in being an exotic type of synthesis or unusual electronically. It is special because Ken had the sensibility to include such musical features.

I'm going to try to finish my two this morning! I got sidelined the past two weeks by water in my basement. Here goes!

You can use the CV processor to alter the effect of CV signals - for example, usually a rising voltage increases the frequency/pitch of the output signal. The CV processor can cause the opposite effect - rising voltage = pitch goes low.
I love'em and always use these on my CGS VCOs, the 1V/Oct inputs are just spares. In fact, 8 of my CGS VCOs only have the CV processor inputs and no 1V/oct at all

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